Such methods are known for example from U.S. Pat. Nos. 5,600,766 and 6,023,761.
U.S. Pat. No. 5,600,766 describes the compressed storage of a graphic image in PROM, initialization of a power-on self test, decompression of the graphic image, copying of the decompressed graphic into RAM, and display of the decompressed graphic during the self-test.
U.S. Pat. No. 6,023,761 describes a decompression algorithm, which together with a main program is stored in a non-volatile memory. The decompression algorithm decompresses pre-allocated data of the main program and copies it into the volatile memory. The main program, which exists in uncompressed form, remains in the non-volatile memory.